Health Level Seven (HL7) is a standards-producing body, which develops data standards for storing and exchanging information across the healthcare industry. The HL7 standards cover both clinical and administrative aspects of the healthcare industry, including laboratory, clinical genomics, medical records, patient care, pharmacy, public health reporting, regulated studies, accounts and billing, claims and reimbursement, patient administration and personnel management scheduling.
Starting from version 3 of the HL7 specifications (commonly referred to as HL7 V3), all HL7 messages and data structures are specified and implemented as hierarchically-structured eXtensible Markup Language (XML) documents. All data structures are derived, using a well-defined methodology, from a single Reference Information Model (RIM). The RIM provides an explicit representation of the semantic and lexical connections that exist between the information items carried in the fields of HL7 messages. Further details regarding the HL7 organization and specifications are available at www.hl7.org.
As part of the processing of HL7 messages in healthcare-related computer systems, it is often desired to store the information carried in HL7 messages and documents using a relational database management system (RDBMS). Exemplary RDBMSs include DB2® produced by IBM Corporation (Armonk, N.Y.), Oracle® produced by Oracle Corporation (Redwood Shores, Calif.) and Microsoft® Office Access produced by Microsoft Corporation (Redmond, Wash.). Information regarding these products can be found at www-306.ibm.com/software/data/db2/, www.oracle.com and www.office.microsoft.com, respectively.
Several methods are known in the art for converting object models and hierarchical data structures into relational database schemas, while preserving the structure and interrelationships between data items. For example, Ambler describes such methods in “Mapping Objects to Relational Databases,” www-106.ibm.com/developerworks/webservices/library/ws-mapping-to-rdb, July 2000. Zhang and Dewey describe a method for converting an HL7 XML document type definition (DTD) into a relational database schema in “Electronic Medical Record Systems and Databases,” icmit.mit.edu/sxzhang/healthcare/word.htm, May 2001.
In addition, several methods and systems for converting object models to relational schemas and for storing XML-structured documents in databases appear in the patent literature. For example, U.S. Pat. No. 6,529,909 describes a method and a system for translating an object attribute to and from a database value. U.S. Pat. No. 6,163,781 describes a system for storing a definitional data table that defines variable symbols representing respective measurable physical phenomena. The definitional data table uniquely defines the variable symbols by relating them to respective data domains for the respective phenomena represented by the symbols. An object-to-relational data converter is used to map object attributes into two relational tables stored in a memory. The system is used for processing, storing, and retrieving of healthcare-related information in very large database systems.
Methods for converting XML DTDs to relational database schemas are also described by Shanmugasundaram et al., in “Relational Databases for Querying XML Documents: Limitations and opportunities.” Proceedings of the 25th Very Large Data Bases Conference (VLDB'99), Edinburgh, Scotland, September 1999, pages 302-314.
Some software tools for performing XML-database conversions are available. For example, SkyHawk Systems (San Jose, Calif.) produce a database middleware package called “Connect XML-2-DB” for transforming and moving data from XML documents to relational databases using mapping files. Another middleware package for transferring data between XML documents and relational databases, called “XML-DBMS,” was developed by Robert Bourret (Felton, Calif.). This middleware package is available at www.rpbourret.com/xmldbms/.